In the oil and gas industry, it is sometimes necessary to provide ground cover mats with sufficient strength to support heavy equipment and transport trucks over wet or disturbed ground.
Several prior art ground cover mats exist; however, they lack sufficient reinforcement to withstand the pressure of heavy equipment and transport trucks, and are expensive to produce. What is needed is an improved ground cover mat which is simple and relatively inexpensive and has sufficient strength and durability to support heavy equipment.
Further, ground cover mats tend to be extremely heavy and lengthy, making the mats difficult to store, lift, transport, assemble or disassemble. Since a series of mats are generally required to construct a temporary road, an improved ground cover mat which is easy to handle is desirable.
There have been attempts in the prior art to solve such problems. For example, U.S. Pat. No. 4,462,712 issued Jul. 31, 1984 to Penland, Sr. describes an interlocking mat assembly comprising assemblies of two-ply laminated mats which interlock and are secured together by nailing a top layer of planks over the interlocked mats. However, this mat assembly is particularly labor intensive.
Canadian Patent No. 1,285,166 issued Jun. 25, 1991 to Pouyer describes a temporary road which includes a plurality of sets, each defined by upper and lower matrices with the upper matrices comprising boards and the lower matrices comprising cross-support members for supporting the boards. The road is constructed by interlocking series of sets in a superimposed assembly, necessitating significant redundancy of effort in assembly and disassembly.
U.S. Pat. No. 6,695,527 issued Feb. 24, 2004 to Seaux et al. describes interlocking mats constructed of two mirror half pieces which are joined together to form a complete single mat containing an internal cellular structure. Traction promoting elements in the form of raised strips extending outward from the planar surfaces of the mats and aligned with the internal cell forming walls are provided to improve traction and to absorb heavy loading from vehicles and equipment. However, Seaux et al. indicates that when a large number of the raised strips are not specifically positioned in such a manner, the relatively thin outer skin defining the roughly planar surfaces of the mats can become easily deformed by such direct loading.
U.S. Pat. Nos. 4,600,336 and 5,087,149 issued Jul. 15, 1986 and Feb. 11, 1992 respectively, to Waller describe mat systems having individual mats with alternating offset extensions and recesses along the edges. These systems are disadvantageous in that the offset extensions are comprised of individual planks which may be subject to warping or splintering when exposed to heavy loads. Further, the offset extensions need to be nailed in place to be secured within the recess of an adjacent mat. An extra plank is secured over the exposed nailed joints of adjacent mats to interlock the mat assemblies together as a roadway, which significantly increases material and labor requirements.
Canadian Patent No. 2,348,328 issued Oct. 22, 2002 to Stasiewich et al describes a road mat including, at both of its ends, couplings having retaining lips which engage complimentary retaining lips of adjacent mats to prevent separation when weight applied by a vehicle to one road mat is transferred to an adjacent road mat. Canadian Patent No. 2,364,968 issued Jun. 22, 2004 to Stasiewich et al describes a road mat having end and side interlocks to secure adjacent mats. However, there is no provision in either patent of details regarding attachment of the retaining lips to the mat ends, or the use of any reinforcing structural support.
Therefore, there is a need in the art for an improved ground cover mat which has sufficient strength to support heavy equipment, provides easy handling, and is simple and relatively inexpensive.